1. Field of the Invention
The present invention relates to method and apparatus for the continuous, automatic production of cross-plied material, preferably for structural or anti-ballistic end uses and preferably for supply in roll form, i.e., like a bolt of cloth, for subsequent processing or use. The present invention also relates to a cross-plied material, especially in rolls, made in accordance with the method and which can be ballistic resistant.
A "ply" is one layer of material, and a "cross-ply" or "cross-plied material" is a plurality of layers of material, preferably only two, which are superimposed with the axes of adjacent layers rotated relative to one another.
2. Prior Art
SPECTRA SHIELD.TM. ballistic resistant armor material, commercially available from Allied Signal Corporation, comprises two layers of unidirectional SPECTRA.RTM. polyethylene fibers in a flexible thermoplastic resin in a 0.degree.,90.degree. fiber orientation. SPECTRA SHIELD material can be incorporated into lightweight body armor or rigid composite armor, with the threat level determining the number of layers of material used. The material is typically delivered to the customer in rectangular, preferably square, sheets which can then be cut and fabricated into a desired configuration. There would be less waste of material, and thus less expense to the customer, if the composite material could be furnished in continuous roll form, i.e., like a bolt of cloth, rather than in squares or rectangles. This would permit the customer to maximize material usage by continuously repeating the pattern to be cut from the continuous length of material and thereby eliminate the scrap formed by using rectangular sheets.
Ballistic resistant articles and fibers conventionally used in them are well known, as taught by, e.g., U.S. Pat. No. 4,403,012, 4,457,985 and 4,916,000, all of which are hereby incorporated by reference.
U.S. Pat. No. 4,623,574, hereby incorporated by reference, discloses the formation of prepreg sheets comprised of elastomer coated high strength fibers which are substantially parallel and aligned along a common fiber direction. The patent teaches that the prepreg sheets can be plied together, with successive sheets being rotated relative to the first sheet, to form simple composite materials. These composite materials are of a given size, e.g., 12.times.12 inches (4.7.times.4.7 cm), and are individually molded prior to being sent to the customer. This patent is exemplary of the prior art represented by the SPECTRA SHIELD material discussed above.
U.S. Pat. No. 3,992,240, hereby incorporated by reference, teaches method and apparatus for mass production of an elongated multiple ply laminated structure of variable cross section. The plies are resin impregnated fiber plies which are brought into longitudinal alignment, combined and laminated.
The present invention, which was developed in an attempt to overcome the deficiencies of the prior art, provides a cross-plied material by a continuous, automated method.